The present invention relates to a tool assembly comprising a tool body such as a boring bar, and an adjustable machining tool cartridge attached thereto that provides improved adjustment of the cutting diameter of the tool assembly.
A cutaway view of a conventional tool assembly is depicted in FIGS. 4 and 5. The cutting end of a boring bar 1 is illustrated, the other end of the boring bar being understood to be attached to the main shaft of a boring machine or CNC machine via a tapered shank or the like. Boring bar 1 is provided over an area thereof with a recess 3 having a flat side wall 5 and bottom wall 7.
A tool cartridge 9 comprises a cartridge chassis 11; the chassis is fixed to boring bar 1 by means of a clamping screw 15 threaded into a screw hole 13 formed in the boring bar. Into cartridge chassis 11 is threaded in the axial direction an adjustment screw 17; rotation of this screw in the extending direction fills the space between the cartridge chassis and the end wall 6 of the recess while at the same time supporting chassis 11 with strong force from the end wall.
Cartridge chassis 11 has a cutting tip 19 mounted thereto by a known method. Cartridge chassis 11 is provided, in proximity to the distal end thereof, with an adjustment screw 21 threaded into a screw hole in chassis 11, this adjustment screw being positioned so as to abut the side walls 5 of recess 3.
With this known design, advancing adjustment screw 21 causes cartridge chassis 11 to undergo elastic deformation whereby the outmost end of the cutting tip undergoes radial outward-directed displacement, allowing the machining diameter for the boring operation to be changed.
With the conventional tool cartridge 9 described above, since the machining diameter is changed via elastic deformation, the scope of adjustment thereof is naturally limited; typically, machining diameter can be adjusted between about 0.1 and 0.4 mm, with larger tool cartridges designed for greater elastic deformation giving a range of about 0.5 to 0.7 mm. Accordingly, there is a need for a tool cartridge affording a wider range of adjustment of machining diameter in order to meet dimensional requirements for various workpieces using an existing tool cartridge mounted on the boring bar or other similar tool.
The present invention is directed to a tool assembly comprising a tool body, for example a boring bar or the like, and a tool cartridge supporting a cutting tip and attached to the tool body that overcomes the limitations of the prior art and provides improved adjustment of cutting tip edge position. This invention may be beneficially used in mills, multiple action tools, boring bars and other tools known in the art.
An object of the present invention is to provide a tool assembly comprising a tool body, such as a boring bar, a tool cartridge having a chassis and supporting a cutting tip, a pivot secured to the tool body for engaging the tool cartridge, an adjustment means, and a spring means, wherein the tool cartridge chassis is pivotably attached to the tool body, the adjustment means is positioned to a first side of the pivot and in abutment with a surface of the tool body, and the spring means positioned on a second side of the pivot is interposed between the tool body and the chassis.
It is a further object of the invention to provide an adjustment means for transmitting force to a portion of the cartridge chassis so as to impart a radial outward-directed rotational force thereto positioned on a first side of the pivot and a spring means for imparting to the cartridge chassis a rotational force in the direction opposite the first rotational force positioned on a second side of the pivot. It is a further object that the adjustment means and the spring means allow fine adjustment of positioning of a cutting tip on the chassis through control of the chassis"" rotation about the pivot.
A further object of the present invention is to provide a boring bar wherein the chassis of the tool cartridge is pivotably attached within a recess formed in the boring bar; an adjustment screw is provided to a first side of the pivot axis, being threaded into the cartridge chassis and situated in abutment with a surface of the cutting bar; and a tensioning device, such as a compression spring, is provided to a second side of the pivot axis, interposed between the boring bar and cartridge chassis. With this design, appreciable pivotal motion can be imparted to the cartridge chassis by loosening or tightening the adjustment screw, thereby providing a wider range of adjustment than the prior art.
Another object of the present invention is to provide a tool body, for example a boring bar wherein the chassis of the tool cartridge is pivotably attached within a recess formed in the boring bar and is actuated by a draw-bar. The draw-bar displaceable in the lengthwise direction is provided to the interior of the boring bar for adjusting tool cartridge position. This draw-bar is provided, to a first side of the pivot axis of the cartridge chassis, with a main cam action device for transmitting force to a portion of the cartridge chassis so as to impart radial outward-directed rotational force thereto; a tensioning device, such as a compression spring, for imparting to the cartridge chassis rotational force in the direction opposite the previous rotational force is provided to a second side of the pivot axis; and the pivoting position of the cartridge chassis is adjustable by means of adjustment of the longitudinal position of the draw-bar in relation to the boring bar. With this design, tool cartridge pivoting position can be adjusted automatically over a wide range. A further object of the invention is to provide a tensioning device, such as a compression spring, interposed between the boring bar and cartridge chassis, thus providing a simple design. A yet further object of the invention is fine adjustment of cartridge chassis pivoting position made via an adjustment means such as a screw, cam, wedge, and the like, whether mechanical, hydraulic or pneumatic.
Alternatively, another further object of the invention is to provide a compression spring interposed between the draw-bar and the cartridge chassis. The draw-bar includes an auxiliary cam action device whereby the degree of compression of the compression spring between the auxiliary cam action device and the cartridge chassis remains unchanged irrespective of the pivoting position of the cartridge chassis imparted by the main cam action device. Thus, the force produced by the compression spring remains constant regardless of the pivoting position of the cartridge chassis so that the degree of change in position of the cutting tip due to centrifugal force is unaffected by the pivoting position of the cartridge chassis.
A further object of the invention is to provide a follower rod provided between the main cam action device and the cartridge chassis; and an adjustment screw threaded into the cartridge chassis so as to abut the follower rod.
It is a yet further object of the invention to provide a boring bar wherein the recess is a groove formed coextensive with the lengthwise extension of the boring bar so as to have two side walls, and the cartridge chassis is pivotably supported by a pin supported on the two side walls. This arrangement provides reliable pivotal support.